The present invention relates to an active-matrix liquid crystal display device having a property to be able to repair disconnection (open failure) in a bus line and relates to a method of fabricating the same. More particularly, the present invention relates to patterning of lines for repair (hereinafter referred to as repair lines) provided on the periphery of a thin film transistor (hereinafter referred to as TFT) array substrate so as to eliminate or repair a display defect which occurs in a display area when a bus line disconnects or has open failures and relates to a method of pattern processing of repair lines.
By adopting an active matrix type, a liquid crystal display device (hereinafter referred to as a liquid crystal display) has enabled displaying function which is not inferior to that obtained by a cathode ray tube.
The active matrix liquid crystal display (hereinafter, referred to as AM-LCD) with fine resolution and enlarged display size is expected and is being brought to the commercial stage.
However, it is inevitable that the number and the lengths of the bus lines increase as the size of the AM-LCD becomes large.
It is therefore supposed that the occurrence of disconnection in bus lines increases but it has been very difficult to fabricate an enlarged AM-LCD having no disconnection.
As for such disconnection, AM-LCDs having the property to be able to repair a disconnection in a case in which such disconnection in a bus line occurs, are under development.
The conventional AM-LCDs having the property to be able to repair disconnection are disclosed, for example, in Japanese Unexamined Patent Publication Nos. 23425/1991, 85525/1991, 98023/1991, 259222/1991 and 37824/1992.
However, the examples disclosed in these above publications are all directed to a case in which tape carrier packages (TCPs) are mounted on the an upper side and a lower side of source lines. Thus, in a case in which a TCP is mounted on only one side it is required that a line for repair (a repair line) is provided on the unmounted side terminal portion where the TCP is not mounted, so that the repair line is available to be connected for each TCP.
In this case, to each TCP, the repair line is necessary to be drawn around outside with minimizing capacity as small as possible to the utmost.
Thus, the repair lines are usually designed so as to be provided without intersecting other lines. Therefore, in a case when the whole line pattern is divided and divided line patterns are arranged for divisional exposure by a pattern exposure system, each divided line pattern is provided as one which is different from each other. Thus, it is required to prepare numerous line patterns, and numerous masks (reticles).
Further, because the number of mask (reticle) changes is numerous, there is a problem that exchanging masks causes productivity to be deteriorated.
The term "TCP" is defined and explained as follows for example in a publication "Flat Panel Display '95 (Nikkei Micro Device separate volume, Nikkei BP Company)" on page 234: "A flexible tape on which a drive IC is mounted by means of gang bonding is referred to as a TCP and the technique is referred to as tape automated bonding (TAB). A connection pitch, configuration and flexibility in mounting such as a structure having opening and a structure capable of bending are the features. The TCP may be recognized to be suitable mounting form for a refined connection pitch and for a module design with slim profile, reduced weight and compact size, where a liquid crystal panel is enhanced in capacity, resolution and display in color. Further, the configuration according to an embodiment in which such a TCP is mounted is illustrated in FIG. 15 on page 233 of the above publication. Still further, summarized explanation relating to TAB mounting is also introduced in a publication "Monthly Display" Vol. 8, 1996 on pages 19 to 31. Hereinafter, detailed explanation concerning "TCP" is omitted.
FIG. 3 is a schematic drawing illustrating arrangement of repair line (that is, a line for repair) in a conventional matrix liquid crystal display (AM-LCD).
In the drawing, numeral 1 denotes a TFT array substrate, numeral 2 denotes a TCP provided on the source side (hereinafter, referred to as a source side TCP) on which a drive circuit IC provided on the source side (hereinafter, referred to as a source side drive circuit IC) is mounted, numeral 3 denotes a TCP provided on the gate side (hereinafter, referred to as a gate side TCP) on which a drive circuit IC provided on the gate side (hereinafter, referred to as a gate side drive circuit IC) is mounted, numeral 4 denotes a peripheral printed circuit board (or PCB) provided on the source side periphery (hereinafter referred to as a source side peripheral printed circuit board), numeral 5 denotes a peripheral printed circuit board provided on the gate side periphery (hereinafter, referred to as a gate side peripheral printed circuit board), numeral 6 denotes a disconnection portion, numeral 7 denotes a first connection point, numeral 8 denotes a second connection point, and numeral 9 denotes a repair line.
According to the conventional art, a line (that is, a repair line for connecting a disconnection portion in a bus line) to be connected from the underside (in the drawing) as shown in FIG. 3 is, for example, routed to a terminal in the opposite side of ten pieces of the source side TCP 2, every two of the lines being routed in pairs, the repair lines being provided in each individual pattern.
A method of repair in a case in which a disconnection in a bus line occurs is described below. For example, in case when a line is disconnected at disconnection portion 6 shown in FIG. 3, the intersecting portion where two lines which are denoted by numerals 7 and 8 intersect each other will be irradiated by laser light to be melted. As the result, two lines will be connected at the intersecting portion. Therefore, a signal input from the opposite side in such a manner that the signal input is transmitted from the source side TCP 2, via the source side peripheral circuit 4 and the gate side peripheral circuit 5, to the repair line 9 through electrically connected circuits is possible.
Because, as shown in FIG. 3, five areas for exposing (exposure areas) F to J in the conventional art which are related to repair lines 9 are arranged as individually configured repair lines different from each other, the repair lines 9 are provided by forming individually configured line patterns different from each other.
In a case in which in a photolithography processing step, by using a pattern exposure system for example "FX-501D series" supplied by NIKON CORPORATION, a whole line pattern on TFT substrate 1 is divided and divided line patterns are exposed one by one, the size of an effective area in a rectangle (length of the diagonal line is 14 cm, long side is 13 cm) is about 10 cm.times.10 cm. Further, the number of masks exchangeable with high speed is six or less at most.
However, as shown in FIG. 3 the number of exposure areas on the TFT array substrate 1 is ten denoted by A to J.
While areas denoted by B, C and D are arranged in the same configured line patterns, the line patterns for other exposure areas are different from each other. Thus, in a case when a display area of the TFT array substrate 1, the size of which is over about 15", is exposed, the number of necessary masks exceeds inevitably 6 because each necessary mask must cover both the inside of the display area and the peripheral area. Therefore, the productivity deteriorates and designing a mask is complicated.
As described above, since a plurality of patterns of exposure areas covering the repair lines (lines for repair) in the conventional matrix liquid crystal display device are formed by using patterns different from each other, each pattern requires a pattern different from the others. Therefore, in a case in which line patterns are provided by divisional exposure by using an exposure machine because the number of masks increases and the number of exchanging masks increases, there is a problem that the productivity deteriorates.